Generally, in the process of manufacturing a semiconductor element, an acceleration test is performed in which a temperature or voltage load is applied, that is, a burn-in test is performed. As a result of the burn-in test, when the value of a characteristic of a certain semiconductor element fails to satisfy a prescribed reference value, that semiconductor element is removed from a group of non-defective components as an initial-stage defective component.
In a vertical cavity surface emitting laser element, light is emitted in a direction orthogonal to a semiconductor substrate. Consequently, a burn-in test can be performed in a wafer state where a plurality of vertical cavity surface emitting laser elements are formed in an array pattern. This type of burn-in test is called wafer level burn-in (WLBI).
There is a demand for techniques for performing WLBI on a vertical cavity surface emitting laser array with accuracy and at low cost. In a surface emission wafer disclosed in Japanese Unexamined Patent Application Publication No. 2006-66845 for example, a plurality of surface emission elements are connected in series in such an orientation that the forward directions of light-emitting element units match.